Team # 1584 Page 5 of 18
1.4 The application of biomechanics in the design of the seat backplate
Biomechanical analysis shows,when the angle between the seat and the backrest is between
90 ° -120 °,the shear force between seat and Ischial tuberosity can be completely
eliminated.At this time buttock don’t has sliding trend. In this case, we do force analysis of
vertebrae and intervertebral disc will consider three main force, force pressure on vertebra
and intervertebral disc, shear force and the stress when intervertebral disc bending. According
to the experience, when the vertebra suffered smaller force and bending moment, people will
feel more comfortable.
2. The Description of Problem
After researching on the problem, we believe that the key to solving problems is obtaining
the optimal curve of the seat backplate, in order to achieve the airplane’s goals that they can
take advantage of the "slimline" seats without changing the main internal structure and at the
same time make the seat more comfortable. Secondly, we will write an advertising material,
to introduce the features and advantages of our design of this "slimline" seats.
2.1 The optimal seat backplate curve
Set an appropriate seat backplate curve can reduce back tension, so that passengers will be
more comfortable during the voyage.
The body will feel most comfortable when the body back vertebra is in a natural form, to
achieve this, the shape of the seat should be consistent with the natural curvature of the
vertebra. So, if the seat backplate curve is close to the human ecological curve, it will make
the ride comfort greatly improved.
To measure comfort,we consider the human body in different positions, the size of the
compressive force, shear force and bending moment that the everywhere of the vertebra bear,
established a mathematical model about the resulting physical discomfort. The focus is to
analyze the force conditions of the 24 vertebra and Intervertebral disc(in this case the series of
angle between them and vertical direction are different): Respectively stress analysis for the
rigid cylinder vertebra and elastic disc, at the same time use the recursive method, then the
shear force ,bending moment and compressive force on each vertebra and intervertebral disk
are obtained ,then respectively summing three physical quantities as total shear force, total
bending moment and total compressive force. Then we will summing the total shear force,
total bending moment and total compressive force as the value of discomfort at that time.
While the lowest value of discomfort corresponding to a set of angle which can be uniquely
determined by the bending status where the composition of forces on the vertebra is smallest.
Through finding optimal solution and fitting the data, we can find a smooth curve. This
curve is not only the curve of vertebra when it is most comfortable, but also can be seen as the
seat back plate curve that can make passengers most comfortable. As a result, we can get the